When Firefox hangs, it stops responding to your clicks and keystrokes and doesn't seem to be doing anything. Also, a "(Not Responding)" label is displayed in the title bar and the mouse cursor becomes a spinning wheelhourglass when it's over the Firefox window.Also, the mouse becomes a spinning wait cursor when it's over the Firefox window. This article gives you solutions to Firefox hangs depending on when they happen.

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Consider using it before going through a lengthy troubleshooting process.

The Refresh Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Consider using it before going through a lengthy troubleshooting process.

Note: If you send performance data, Mozilla will gather data including hangs for your Firefox, which will help making Firefox better for future versions.

Warning: This will clear your browsing history and remove bookmarks of the day.

Open your profile folder:

At the top of the Firefox window, click on the Firefox button, go over to the Help menuOn the menu bar, click on the Help menuAt the top of the Firefox window, click on the Help menu and select Troubleshooting Information. The Troubleshooting Information tab will open.Click the menu button
, click help
and select Troubleshooting Information. The Troubleshooting Information tab will open.

Under the Application Basics section, click on Show FolderOpen FolderShow in FinderOpen Directory. A window with your profile filesfolder will open.

At the top of the Firefox window, click on the Firefox button and then select ExitAt the top of the Firefox window, click on the File menu and then select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit.

Click the menu button
and then click ExitQuit
.

Wait until Firefox has completely quit.

In the Firefox profile folder, find and rename the files places.sqlite to places.sqlite.old and places.sqlite-journal to places.sqlite-journal.old (if it exists).

To rename a file, right-click on it and select rename from the menuclick on it once to select it and then click a second time on the file name to make it editable. Then add .old to the end of its name.

Finally, reopen Firefox.

When Firefox reopens it will create a new places database. Your browsing history will be lost but Firefox will automatically import your bookmarks from the most recent backup file.

Turn off hardware acceleration

With some graphics card and graphics driver setups, Firefox may hang when using hardware acceleration. You can try turning off hardware acceleration to see if it fixes the problem.

At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.

Click the menu button
and choose Options.Preferences.

Select the Advanced panel and the General tab.

Uncheck Use hardware acceleration when available.

At the top of the Firefox window, click on the Firefox button and then select ExitAt the top of the Firefox window, click on the File menu and then select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit.

Click the menu button
and then click ExitQuit
.

Start Firefox the way you normally do.

If the problem is no longer happening, then hardware acceleration was likely the cause. You can try updating your graphics drivers to see if that fixes it or simply run without hardware acceleration.

Delete duplicated Session Restore files

Firefox may be slow to respond or hang if multiple copies of its Session Restore file have been created:

Open your profile folder:

At the top of the Firefox window, click on the Firefox button, go over to the Help menuOn the menu bar, click on the Help menuAt the top of the Firefox window, click on the Help menu and select Troubleshooting Information. The Troubleshooting Information tab will open.Click the menu button
, click help
and select Troubleshooting Information. The Troubleshooting Information tab will open.

Under the Application Basics section, click on Show FolderOpen FolderShow in FinderOpen Directory. A window with your profile filesfolder will open.

At the top of the Firefox window, click on the Firefox button and then select ExitAt the top of the Firefox window, click on the File menu and then select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit.

Click the menu button
and then click ExitQuit
.

Locate and delete the sessionstore.js file and any copies, such as sessionstore-1.js, sessionstore-2.js.

Change the PAC implementation

If you're using a proxy auto-config file (PAC), Firefox may hang when you attempt to load sites that don't exist or that you haven't opened recently. To determine if you use an automatic proxy configuration file:

At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.

Click the menu button
and choose Options.Preferences.

Select the Advanced panel.

Select the Network tab.

Click Settings…. The Connection Settings dialog appears.

If Automatic proxy configuration URL is selected, you are using an automatic proxy configuration file. Do not disable this setting, which will prevent you from accessing the Internet. Instead, provide this workaround to your network administrator.

Firefox hangs after using it for a long time

Update Firefox

Restart Firefox

Firefox may hang if left open for long periods of time. To fix the issue, restart Firefox.

If you regularly leave Firefox open so that you return to where you left off, you may want to use Firefox's Session Restore feature. For more information, see Configuring session restore.

Firefox hangs while loading the first window

Speed up Session Restore

If you have many tabs to restore, Firefox may hang while loading those sites. Make sure that Don't load tabs until selected is checked in your Tabs settings so that only the last selected tab is loaded at startup.

At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.

Click the menu button
and choose Options.Preferences.

Select the General panel.

Make sure that Don't load tabs until selected is checked.

Firefox hangs when downloading files or saving images

If Firefox hangs when you attempt to download a file or save an image, try these solutions:

Clear download history

Firefox may hang when downloading files if your download history has grown too large. To clear the download history:

Click the Downloads button
and then click Show All Downloads. The Library window will open.

Click Clear Downloads to delete the download history.

Download some sample files to see if the hanging has stopped.

Choose a different download folder

Firefox may hang if the last download folder location (e.g. a shared volume or USB drive) is no longer available. To fix this:

At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.

Click the menu button
and choose Options.Preferences.

Select the General panel.

In the Downloads pane, select Save files to and click the Browse button.

In the Browse For Folder window, choose a new folder location.

Click OK to close the Options window.Click Close to close the Preferences window.Close the Preferences window.Close the about:preferences page. Any changes you've made will automatically be saved.

See if you are now able to download files or save images. If this works, you can go back to your Firefox settings, if you wish, and select Always ask me where to save my files.

Firefox hangs when you quit it

Sometimes when you close Firefox, it may stop responding and remain in memory, even though no Firefox windows are open. This can prevent Firefox from working properly the next time you open it or you may see a "Close Firefox" dialog box with an error message, Firefox is already running, but is not responding.A copy of Firefox is already open. You must then end all Firefox processes or restart the computer before you can reopen Firefox (see "Firefox is already running but is not responding" error message - How to fix it for other causes and solutions).

Close Firefox completely

At the top of the Firefox window, click on the Firefox button and then select ExitAt the top of the Firefox window, click on the File menu and then select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit.

Click the menu button
and then click ExitQuit
.

Close any remaining dialog boxes or secondary windows such as the Downloads window.

If Firefox processes that remain in memory at exit are a recurring problem, try the following solutions.

Troubleshoot your Internet security software

Interactions between certain Internet security software (firewall, anti-virus software) is reported to cause hangs on some systems. You can try to configure your firewall to see if it helps the hang go away.

Firefox hangs when Windows resumes from hibernation on Thinkpad

When resuming Windows from hibernation and Firefox hangs for several minutes it might be due to an issue of the pre-installed "ThinkVantage Technologies Power Manager 6". One option to solve this is to uninstall the software. Another option is to check for a later version of the software on the Lenovo support website and see if that fixes the problem. See Bug 1106202 for more details.